1. Field of the Invention
This invention relates to a piezoelectric transducer for converting electrical energy into ultrasonic wave energy.
2. Description of the Prior Art
Several examples of piezoelectric transducers are known in the prior art. In connection with such transducers it is known generally that the transducer operates over a range of frequencies adjacent to its "resonant" frequency, which is a function of the thickness of the transducer body and the type of material. U.S. Pat. No. 3,179,823 to Nesh describes a transducer having a wedge-shaped body, which, because of its varying thickness is resonant over a broad band of frequencies. The device is primarily intended to absorb and detect ambient vibratory energy in missiles and rockets. Energy is received from a direction normal to one of the flat surfaces 5 or 6, regardless of the frequency. Hence, the transducer has fixed, unidirectional radiation and reception patterns.
The transducer disclosed in U.S. Pat. No. 3,937,467 to Cook et al. is useful in sonar applications. "Teeth-like" projections of varying lengths give the transducer its broadbanded response. The radiation pattern shown in FIG. 15 spans approximately 180.degree. in the horizontal plane over the entire frequency range. Although a curved surface is described in FIGS. 5 and 6, the reference does not attribute special directional characteristics to this configuration.